In treatment of cardiac infarction or stenocardia, for example, a method of forcing open a lesion part (stenosed part) of a coronary artery by a balloon catheter is practiced. Improvements of stenosed parts formed in such biorgans as other blood vessels, bile duct, trachea, esophagus, urethra, nasal cavity and other organs may also be performed in the same or similar manner. A balloon catheter is, in general, configured to have an elongated shaft and a balloon which is disposed at a distal portion of the shaft and is inflated radially. With a preceding guide wire inserted and passed in the balloon catheter, the balloon catheter is sent to the stenosed part in the body.
In such a treatment method, in order to prevent stenosis that causes stenosis again after the treatment of the stenosed part, it has been proposed in recent years to coat the outer surface of the balloon with a drug having a restenosis-preventing effect. On the other hand, in order to prevent the drug on the balloon from being peeled off due to frictional contact (mutual rubbing) between the drug and a blood vessel inner wall during delivery of the balloon to the stenosed part, consideration has been given to providing a sheath as a protective cover for covering the balloon. An example is disclosed in Japanese Application Publication No. 2001-514936 (JP-T-2001-514936).
When a sheath configured as described in Japanese Application Publication No. 2001-514936 is adopted as the protective cover for covering the drug applied on the balloon, a problem that arises involves peeling of the drug off the outer surface of the balloon due to rubbing of the inner circumferential surface of the sheath and the drug against each other at the time of retracting the sheath.